Desulfurization process employing metallic sodium on an inert carrier



Sept.

W. G. MAY ET AL DESULFURIZATION PROCESS EMPLOYING METALLIC SODIUM ON AN INERT CARRIER Filed April 21, 1955 WALTER 6. MAY RAYMOND W. WINKLER HENRY J. OGORZA OIL INVENTORS LY 511/0. (27W ATTORNEY United es Patent C DESULFURIZATION PROCESS EMPLOYING METALLIC SODIUM ON AN INERT CAR- RIER Walter G. May, Union, Raymond W. Winkler, Linden, and Henry J. Ogorzaly, Summit, NJ., assignors to Esso Research and Engineering Company, a corporationof Delaware process for the removal of sulfur compounds from hydrocarbon oils containing the same utilizing metallic sodium.

The invention is more particularly concerned with anintegrated desulfurization process wherein the sodium is maintained on an inert carrier.

It is well known in the art to remove objectionable sulfur compounds from petroleum hydrocarbon fractions using various procedures. In general, these sulfur compounds may be generally classified as mercaptans, disulfide, polysulfides, hydrogen sulfides, thiophenes and various alkyl and cyclic sulfides. These sulfur compounds are objectionable in petroleum oil as, for example, gasolines, kerosenes, heating oils and the like since they tend to lower the storage stability of these fractions. In addition, the sulfur compounds in motor fuels tend to increase the tendency of the motor fuels to form objectionable deposits within the internal combustion engine when burnt.-

In addition, these sulfur compounds have an adverse effect on the octane number response of the motor fuel to the addition of tetraethyl lead. In accordance with the present inventiont an improved integrated operation is employed for the removal of these objectionable sulfur compounds from hydrocarbon fractions utilizing metallic sodium. While it has been known that hydrocarbon fractions can be desulfurized utilizing metallic sodium, it has been the experience that when metallic sodium is used a high boiling sticky residue is formed on the sodium which markedly impairs its eificiency. This is particularly the situation when desulfurizing cracked fractions such as a catalytic naphtha fraction boiling in the range from about 100 F. to 450 F.

In accordance with the present invention the desulfurization reaction is carried out in a fluid bed wherein the sodium is finely dispersed on an inert carrier such as sodium carbonate (Na CO In this operation the naphtha vapors are employed to maintain the fluidized bed which comprises the sodium and the carrier. Under these conditions a very complete desulfurization process is secured. Furthermore, the sticky polymer which tends to form on the fluid bed is removed by burning in a regenerator. Thus, the efiiciency of the reagent is maintained to a very high degree. Also under the particular conditions of the operation a certain build-up of this objectionable sticky material on the solids can be tolerated. However, excessive build-up of the polymer on the fluidized solids causes the bed to bog down. The fresh sodium is distributed in a fine dispersion on the inert carrier. The sodium cannot be added to the solids in the reactor bed as it will not stick to the polymer present on the surface of the carrier. Thus, provision is made for adding the sodium to the regenerated reagent before the mixture enters the desulfurization zone.

The integrated process of the present invention may be more fully understood by reference to the drawing illustrating one embodiment of the same.

Referring specifically to the drawing, a feed hydrocarbon fraction comprising a catalytically cracked napht 2 tha boilingin the range from about 100 to 320 F. is introduced into the system by means of feed line 1. The feed is first passed through a water settling zone 2 where in any entrained water segregates and is withdrawn as a water phase by means of line 3. The dehydrated feed is passed through a series of heat exchanging zones 4, 5 and 6 by means of pump 7. The feed is heated to the desired temperature in furnace 8 and introduced as a vapor into the bottom of desulfurization zone 10 by means of line 9. In desulfurization zone 10 the upflowing feed passes serially through two distinct fluidized beds 11 and 12 maintained on the top of suitable pierced plate elements. The fluidized solids comprising finely divided metallic sodium deposited on an inert carrier passes from zone 12 to zone 11 by'means of downflow 13. The desulfurized product passes upwardly in zone 10 through a cyclone element 14 which may comprise any number to return these particles to lower bed 11, thus by-passing upper catalyst bed 12. Desulfurized vapors free of sulfur and sodium are removed from zone 10 by means of line 16, passed through heat exchanging zone 6 and introduced at a mid-pointof a scrubber-cooler zone 17. This scrubber-cooler 17 is used to remove the remaining entrained solids from the vapor stream at the dew point. The vapor stream, completely free of entrained reagent and sulfur compounds, is removed overhead from zone 17 by means of line 18, passed through heat exchanging zone 4, cooler 19 and introduced into treated naphtha storage zone 20. This treated desulfurized naphtha may be withdrawn from product storage zone 20 by means of line 21 and further treated or handled as desired.

A heavy slurry fraction containing reagent is removed from the bottom of zone 17 by means of line 22 and pumped to line 23. This fraction is passed through heat exchanging zone 5 and mixed with water which is introduced by means of line 24. A portion of the slurry, prior to mixing with water, is preferably recycled to zone 17 by means of'line 25. The slurry-water mixture is passed through a water mixng zone 26, withdrawn by meansof line 27 and passed to a slurry settler 28. Uncondensed gases are withdrawn from zone 28 by means of line 29. A re-run oil phase is segregated in trough ele ment 30 and withdrawn from the system by means of line 31. The sulfides are removed from zone 28 by means of line 32 and handled or disposed of as desired.

The spent solid reagent phase is Withdrawn from the bottom of desulfurization zone 10 by means of line 33 and introduced into the bottom of regenerator 34. Air is mixed with this stream by means of line 35 while oil is introduced into zone 34 by means of line 36. The reagent is regenerated in zone 34 at a temperature of about 800 F. to 1200 F., preferably at about 1000 F. Combustion vapors flow upwardly in zone 34, pass through cyclone separator 37 and are "Withdrawn from the system by means of line 38. Reagent particles are returned to the fluid bed in zone 34 by means of line 39.

The regenerated reagent is removed from zone 34 by means of line 40 and passed to a sodium mixing zone 41 maintained in zone 10. Molten sodium is introduced into zone 41 by means of line 42 while nitrogen is introduced by means of line 43. Thus, in zone 41 a fine dispersion of sodium is secured on the inert carrier to continuously produce the present reagent.

In accordance with the invention the sodium is introduced from a tank car or equivalent 50. The sodium is maintained in a liquid state by recycling an oil stream. The oil is withdrawn preferably from a heating oil storage zone 51, passed through a heat exchange zone 52 by means of pump 53 and thence through a coil 54 so as to melt the sodium. heating oil is returned to zone 51 by means of line 55. Liquid sodium is removed overhead from jz'ohe 50 by means of line.56 and passed to a sodium receiver 57. A suitable seal 58 is maintained on zone 57, The sodium is passed to a sodium storage zone 59 by means of line 60. The sodium is maintained in the molten condition by means of a second heating coil element 61 circulated from zone 51. The molten sodium, 'at a temperature in the range from about 250 to 400 F. is introduced into reagent preparation zone 41 by means of pump 62 and line 42. The sodium in zones 59 and 501s maintained under an atmosphere of nitrogen which is introduced from zone 70 by means of line 71 and line 72.

The process of the present invention may be more fully understood by the following example illustrating the same:

Example Feed Product Percent Sulfur 0.124 e. 005 Research Octane:

Clean 91.7. 90. 9 2 cc. TEL 96. 8 97. 3

Yield Loss -Z%. Sodium Consumption -1.45 lbs.'lbbl,

The process of the present invention comprises an over all integrated operation for the desulfnrization of hydrocarbons utilizing metallic sodium dispersed on an inert carrier. While the preferred carrier comprises sodium carbonate other carriers such as coke, alkali metal sulfates such as sodium sulfate and alumina may be employed. The amount of sodium dispersed in the reagent 4. is in the range from about 1% to 4 by weight, preferably about 2% by weight. The equilibrium concentration of the sodium in the reactor is in the range from about 0.075 to 0.75% by weight. A preferred concentration in the reactor is in the range from about 0.2% to 0.3% by weight.

The temperature maintained in the desulfurization zone is in the range from about 450 to about 900 F.

A satisfactory temperature is about 500 F.

The temperature of the metallic sodium introduced into reagent preparation zone 41 may bein the range from about 212 F. to 900 F. However, it is preferred to maintain this sodium at a temperature of about 300 F. to 400 F.

What is claimed is:

1. A desulfurization process which comprises dispersing from about 1 to 4 wt. percent of molten sodium upon a particulate inert solid; contacting said particul-ate solid with a vaporized sulfur-containing petroleum distillate at a temperature of from 450 to 900 B, said solid being maintained as a downflowing fluidized bed by upflowing distillate vapor; withdrawing distillate vapor w of substantially reduced sulfur content overhead from said bed; recovering particulate solid essentially free of metallic sodium from the bottom of said bed; burning polymeric deposits from said recovered solid; and recycling said solid free of deposits for the dispersion of molten sodium thereon.

2. A process as defined by claim 1 wherein said particulate solid is finely divided sodium sulfate. I

3. A process as defined by claim 1 wherein the equilibrium sodium content within said fluidized bed is maintained at from about 0.075 to about 0.75% by weight.

4. A process as defined by claim 1 wherein said downfiowing fluidized bed is maintained in two distinct superimposed stages;

References Cited in the file of this patent UNITED STATES PATENTS 1,801,412 Carlisle Apr. 21, 1931 1,859,028 Cross May 17, 1932 1,865,235 Cross June 28, 1932 2,058,131 Carlisle Oct. 20, 1936 2,059,542 Wait Nev. 3, 1936 2,078,468 stratford Apr. 27, 1937 2,481,300 Engel Sept. 6, 1949 

1. A DESULFURIZATION PROCESS WHICH COMPRISES DISPERSING FROM ABOUT 1 TO 4 WT. PERCENT OF MOLTEN SODIUM UPON A PARTICULATE INERT SOLID; CONTACTING SAID PARTICULATE SOLID WITH A VAPORIZED SULFUR-CONTAINING PETROLEUM DISTILLATE AT A TEMPERATURE OF FROM 450 TO 900*F., SAID SOLID BEING MAINTAINED AS A DOWNFLOWING FLUIDIZED BED BY UPFLOWING DISTILLATE VAPOR; WITHDRAWING DISTILLATE VAPOR OF SUBSTANTIALLY REDUCED SULFUR CONTENT OVERHEAD FROM SAID BED; RECOVERING PARTICULATE SOLID ESSENTIALLY FREE OF METALLIC SODIUM FROM THE BOTTOM OF SAID BED; BURNING 